The objective of the proposed collaborative program is to understand the relationship between the optical and mechanical properties of the crystalline lens and the amplitude of accommodation and its loss in presbyopia. The general application of these bioengineering studies is the development of suitable technology including devices and surgical procedures for the restoration of near vision to presbyopes, as well as the restoration of good visual performance to cataract patients. The specific aims of the proposed research are: 1. To measure the mechanical properties of the crystalline lens 2: To measure the mechanical properties of the lens capsule 3: To measure the mechanical properties of the zonules 4: To develop mechanical and optical instrumentation to simulate accommodation in explanted crystalline lenses of eye-bank eyes (lens stretcher) 5: To quantify changes in normal and refilled crystalline lens during simulated accommodation 6: To develop an opto-mechanical model of the lens during accommodation The static and dynamic lens mechanical properties will be measured as a function of age using a micro-Fourier rheometer. The mechanical properties of the capsule will be measured using a custom-made capsule stretching device. The mechanical properties of the zonules will be investigated using atomic force microscopy and tensiometry. An opto-mechanical lens stretching system will be constructed to simulate accommodation on human cadaver lens specimens that include the crystalline lens, lens capsule, zonules, ciliary body and sclera. The system will be used to measure and correlate stretching forces with changes in lens equatorial diameter, thickness, displacement, topography, power and aberrations during simulated accommodation as a function of age. The contribution of the lens capsule and zonules to the mechanics of accommodation will be quantified by conducting lens stretching experiments before and after lens refilling with injectable materials of controlled mechanical properties.